1. Separate the eggs.
2. Mix the flour, baking powder and salt in a bowl.
3. Melt the butter in a saucepan. Whisk the egg yolks in another bowl with a fork and then add milk and butter.
4. Add the flour mixture and whisk with an electric mixer until you have a smooth batter.
5. Clean the whisks thoroughly. In a separate bowl, whisk the egg whites with sugar until peaks form. Carefully fold 1/3 of the whisked egg whites into the batter with a spatula. Gently fold remaining whisked egg whites into the batter.
6. Grease the poffertjes pan with vegetable oil and place on the stove at medium heat. As soon as the pan is hot, scoop approx. ½ tablespoon of batter into each poffertjes circle.
7. Let the poffertjes cook for 1 minute. Scoop about ½ teaspoon of peanut butter into the centre of the batter. Now, scoop sufficient batter on top to seal the poffertjes around the dollop of peanut butter.
8. As soon as the surface starts to show bubbles, quickly flip the poffertjes using two skewers or a fork until the cooked side is facing up.
9. Cook until the bottom is golden brown. Serve the poffertjes with butter and icing sugar.

Tip: Fancy a bit of variety? Substitute the caster sugar with vanilla sugar.